Additive lattice cores for lightweight sandwich structures: thermo-mechanical assessment and numerical modelling of PLA-CF

Abstract

Lightweight lattice structures based on Triply Periodic Minimal Surface (TPMS) geometries are promising sandwich-core candidates due to their high stiffness-to-weight ratio and favorable energy absorption characteristics. Fused deposition modeling (FDM) enables the fabrication of these complex architectures using reinforced thermoplastics such as carbon-fiber-reinforced polylactic acid (PLA-CF). During sandwich manufacturing, lattice cores may experience simultaneous thermal and compressive loads arising from adhesive curing and consolidation processes, making their thermo-mechanical stability a critical design requirement. This study investigates the compressive behavior of FDM-manufactured PLA-CF gyroid lattices with 20% relative density under isothermal loading at 20, 50, and 80 °C. Experimental results showed a pronounced temperature-dependent degradation in mechanical performance. The compressive modulus decreased from 84.23 ± 1.76 MPa at 20 °C to 44.89 ± 4.92 MPa at 50 °C (−47%) and 1.60 ± 0.02 MPa at 80 °C (−98% reduction). Similarly, the compressive strength decreased from 2.68 ± 0.06 MPa to 1.17 ± 0.11 MPa (−56%) and 0.049 ± 0.004 MPa (−98% reduction), accompanied by a transition from stable progressive collapse to severe thermal softening above the glass transition region. A finite element model was developed using nominal tensile properties and calibrated through temperature-dependent lattice-scale correction factors identified from the compression tests. The calibrated model reproduced the experimental thermo-mechanical response, providing a practical predictive framework for preliminary manufacturing-oriented assessment and process design of FDM lattice sandwich cores.